Detection system and method for ice and other debris

ABSTRACT

A system and method for detecting debris on the surface of a member are provided, for example, for detecting ice or other debris on an outer surface of an aircraft. The detection system includes a heating device in thermal communication with the member, an infrared sensing device configured to sense infrared radiation emitted from the member, and a monitoring device in communication with the sensing device. The monitoring device is configured to monitor a change in emission from the member and thereby detect the presence of debris on the surface of the member.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 10/854,691now U.S. Pat. No. 7,784,739, filed May 26, 2004, which is incorporatedherein in its entirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the detection of debris on a surfacesuch as ice on an outer portion of an aircraft and, more particularly,relates to the detection of such debris according to the radiantcharacteristics of the surface and/or the debris.

2. Description of Related Art

The formation of ice and other debris on roadways, bridges, buildingstructures, vehicles, and the like can negatively affect thecharacteristics of those devices. For example, the formation of ice onthe outer surfaces of an aircraft can compromise the performance of theaircraft. For this reason, many aircraft have an ice detector that isused to determine whether ice may have formed on critical portions ofthe aircraft. One typical ice detector includes a probe that extendsfrom the exterior of the aircraft. The probe is actuated to vibrate at apredetermined frequency. As ice or other debris forms or otherwisecollects on the probe, the additional mass of the debris changes thefrequency of vibration. The probe senses this change in frequency and,hence, recognizes that an icing condition exists at the probe. The icingcondition on critical portions of the aircraft, such as the wings andcontrol surfaces, can be inferred to exist when an icing conditionexists at the probe, and a de-icing system can be activated. Forexample, the de-icing system can direct a flow of hot air from theaircraft engines through passages that extend through the wings, engineenclosures, or other portions of the aircraft to melt the ice.Alternatively, the de-icing system can include resistive heatingelements disposed in the wings, engine enclosures, or other criticalportions and configured to heat the critical portions to melt the ice.

Unfortunately, some uncertainty exists in the relationship between theicing condition as measured by the probe and the actual formation of iceon the critical portions of the aircraft. In order to provide a marginof safety to cover this uncertainty, the critical portions of theaircraft are at times heated when ice has not formed on those portionsand to an extent beyond that which is necessary to de-ice them. Thisexcessive heating requires bleed air from the aircraft engines or powerfrom the aircraft electrical system and, therefore, unnecessary fuelconsumption and/or decreased aircraft performance, thereby increasingthe flight costs of the aircraft.

Thus, there exists a need for an improved system and method fordetecting ice and/or other debris that can build up on critical portionsof an aircraft or other devices. Preferably, the system shouldaccurately detect the presence of debris on the critical portions of thedevice so that unnecessary heating or otherwise clearing of thoseportions can be minimized.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a system and method for detecting debrison the surface of a member, e.g., ice on an outer surface of anaircraft, according to the change in the infrared radiation emitted fromthe member, which results from a diagnostic deposition of heat into themember. The presence of debris can be detected accurately and withoutrelying on a correlation with an icing condition that exists at a remoteprobe.

According to one embodiment of the present invention, the detectionsystem includes a heating device in thermal communication with themember, an infrared sensing device, and a monitoring device incommunication with the sensing device. The heating device can be aconventional de-icing system, such as an electrical heating device or asystem for directing hot gases through a passage in thermalcommunication with a wing or another member of an aircraft. The sensingdevice is configured to sense infrared radiation emitted from themember, and the monitoring device is configured to monitor a change inemission from the member and thereby detect the presence of debris onthe surface of the member.

The monitoring device can be configured to compare the change inemission of the member to a predetermined characteristic. Further, thesensing device can be configured to sense infrared radiation emittedfrom a plurality of portions on the surface of the member, and themonitoring device can be configured to detect changes in radiationemitted from the plurality of portions and thereby detect the presenceof debris on the surface of the member at each portion.

The monitoring device can also be configured to control the heatingdevice. For example, the monitoring device can actuate the heatingdevice upon detection of ice on the member. Further, the monitoringdevice can be configured to transmit an electronic signal to a statusindicator device indicating the detection of debris on the member.

According to one method of the present invention, a heating device isactuated and thereby heats the member, a resulting change in theinfrared radiation emitted from the member is sensed, and that change isanalyzed to determine the presence or absence of debris on the surfaceof the member. For example, a profile of the radiation emitted from themember as a function of time can be determined, and that profile can becompared to predetermined characteristic temporal profiles. Thepredetermined profile characteristic can be determined by actuating theheating device when debris is known to exist on the member, sensing theinfrared radiation emitted from the member, and determining theresulting change in the infrared radiation. Further, profiles of theradiation emitted from the member can be sensed and monitored for aplurality of portions of the surface to detect the presence of ice onthe surface at each portion.

The debris can be detected according to the rate of increase in theradiation emitted from the member during and following the heating stepor the rate of decrease in the radiation emitted from the membersubsequent to the heating step. Further, upon detection of debris on themember, an electronic signal can be transmitted to a status indicatordevice, and/or the heating device can be automatically actuated to adebris-clearing mode.

According to one aspect of the invention, the detection method andsystem are used to detect ice on an outer portion of an aircraft. Theheating device and the sensing device can be onboard the aircraft andconfigured to operate during flight or on the ground. Alternatively, thesensing device can be remote from the aircraft and configured to sensethe radiation emitted while the aircraft is on the ground or in flight.In either case, the actuating, sensing, and determining can be repeatedaccording to a predetermined schedule.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Having thus described the invention in general terms, reference will nowbe made to the accompanying drawings, which are not necessarily drawn toscale, and wherein:

FIG. 1 is a plan view illustrating an aircraft with a system fordetecting ice or other debris on the aircraft according to oneembodiment of the present invention;

FIG. 2 is a perspective view illustrating one wing of the aircraft ofFIG. 1;

FIG. 3 is a schematic diagram illustrating the detection systemaccording to one embodiment of the present invention;

FIG. 4 is a graph illustrating the magnitudes and temporal behavior ofdiagnostic thermal energy impulses delivered to the surface to betested, and the magnitudes and temporal behavior of the resultinginfrared radiation signature impulses emitted by the combination of thesurface and any debris accreted thereon, as observed by a detectionsystem such as the detection system illustrated in FIG. 3; and

FIG. 5 is a flow chart illustrating the operations for detecting ice orother debris on a surface according to one embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which some, but not allembodiments of the invention are shown. Indeed, this invention may beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will satisfy applicable legalrequirements. Like numbers refer to like elements throughout.

Referring now to the figures and, in particular, FIGS. 1-3, there isshown a detection system 10 for detecting ice or other debris on anaircraft 50. The application of the detection system 10 of the presentinvention is not limited to aircraft, and it is understood that thedetection system 10 can be used to detect ice or other debris on avariety of members and surfaces. For example, the detection system 10can be used to detect ice on any part of the aircraft 50. Alternatively,in other embodiments of the invention, the detection system 10 can beused to detect debris on a roadway, bridge, aircraft runway, building,space structure, marine or other vehicles, and the like. Further, thesystem 10 can be used for detecting various types of debris includingice, dirt or dust, water, and other materials. Such members emitinfrared radiation in varying magnitudes, and the magnitude of infraredradiation from each member generally varies as a function oftemperature.

As shown in FIGS. 1 and 2, the detection system 10 includes at least oneinfrared sensing device 20 that is configured to sense infraredradiation emitted by a member of the aircraft 50. For example, eachsensing device 20 illustrated in FIG. 1 is configured to sense radiationemitted from a respective wing 52 of the aircraft 50, but in otherembodiments, the sensing device 20 can additionally or alternativelysense emissions from other members of the aircraft 50 such as therudders, elevators, engine shrouds, propellers, and the like. Inaddition, while the sensing device 20 is shown to be an onboard device,i.e., mounted on the aircraft 50, the device 20 can alternatively beremotely mounted. For example, the sensing device 20 can be mounted onthe ground proximate to a runway or hangar for sensing radiationemission from the aircraft 50 while the aircraft 50 is stationary or inmotion. Alternatively, the sensing device 20 can be portable, e.g., ahandheld device that can be held by an operator. In any case, thesensing device 20 can be an infrared camera that senses the infraredradiation emitted from a plurality of portions or points of the wing 52and any debris accreted thereon. In particular, the device 20 can be amulti-pixel device, each pixel configured to sense the radiation emittedfrom a corresponding portion of the wing 52.

As illustrated in FIGS. 2 and 3, the sensing device 20 communicates witha monitoring device 30 that is configured to monitor the infraredemissions from the wing 52. For example, the monitoring device 30 can belocated within the cabin of the aircraft 50 and can be electricallyconnected to the sensing device 20 by wire. Alternatively, themonitoring device 30 can be located integrally with the sensing device20, or the monitoring device 30 can be a remote device configured tocommunicate with the sensing device 20 via radio transmission orotherwise. Where multiple sensing devices 20 are used, such as for thewings 52 of the aircraft 50 of FIG. 1, each sensing device 20 can beconnected to a separate monitoring device 30 or more than one sensingdevice 20 can be connected a single monitoring device 30.

As illustrated in FIGS. 1 and 2, the detection system 10 also includes aheating device 40 in thermal communication with the wing 52. Theillustrated heating device 40 is a conventional de-icing system formelting and thereby removing ice 60 from the wings 52 of the aircraft 50before or during flight. Electrically resistive material 42 is disposedin, on, or near the wing 52, for example, on the inner surface of theleading edge 54 of the wing 52. When used for conventional de-icing, theresistive material 42 is electrically energized, and the resultingthermal energy heats the wing 52 and melts ice thereon. Alternatively,the de-icing system can be a system for directing hot gas, i.e., “bleedair,” from the aircraft engines through one or more passages in thermalcommunication with the wings 52. The use of hot gas and electricalresistive heating for de-icing is described in, for example, U.S. Pat.No. 3,981,466 to Shah; U.S. Pat. No. 5,011,098 to McLaren, et al.; U.S.Pat. No. 5,865,397 to Herrmann; and U.S. Pat. No. 4,741,499 to Rudolph,et al., each of which is assigned to the assignee of the presentapplication, and the entirety of each is incorporated herein byreference.

The monitoring device 30 is configured to monitor changes in emissionradiated by the wing 52, for example, an increase in infrared emissiondue to operation of the heating device 40 or a decrease in infraredemission upon terminating operation of the heating device 40. It isunderstood that infrared energy can also be emitted by ice 60 or otherdebris accreted or deposited on the wing 52, and the total emission fromthe combination of the wing 52 and any ice 60 or other debris thereon isgenerally referred to herein as radiation from the wing 52, even thoughsome of the radiation may originate in the ice 60 or debris. FIG. 4graphically illustrates a time sequence of three thermal input impulses70 delivered to the wing 52, as generated by the heating device 40,e.g., three intervals during which the electrical heating device 40 isenergized. FIG. 4 also graphically illustrates two exemplary resultingemission profiles 80, 90 of radiation coming from the wing 52 of theaircraft 50 during and following the three thermal impulses 70 deliveredby the heating device 40. The first profile 80 is representative of theemission from a wing 52 on which no ice 60 is deposited, i.e., a bare orclean wing. In the illustrated embodiment, the infrared emission of thebare wing rises rapidly upon operation of the heating device 40, peaksshortly after each thermal impulse 70 ends, and subsequently decreases.The second profile 90 is representative of the emission from a wing 52on which ice 60 or other debris is deposited. As shown, the emission ofthe ice-bearing wing is expected to rise less rapidly than that of thebare wing and to rise to a maximum value that is smaller than themaximum value observed in the case of the bare wing. In addition, theemission from the ice-bearing wing can decrease at a slower rate thanthe rate of decreases for the bare wing. For simplicity of illustration,FIG. 4 exhibits a case in which the bare-wing response 80 and theice-bearing response 90 both start from the same baseline, that is thesame equilibrium level of emission as it exists before the diagnosticthermal impulse 70 is applied. However, in other embodiments of thepresent invention, the detection system 10 can compare the profiles 80,90 even if the profiles 80, 90 have different baseline levels.

While the present invention is not limited to any particular theory ofoperation, it is believed that if a thermal impulse 70 is delivered tothe wing 52, the resulting radiation energy observed by the sensingdevice 20 will be different depending on whether the wing 52 does ordoes not carry accreted debris such as ice. Using ice as an example,this difference in observed radiation can result for the followingreasons among others: (a) any ice 60 that has formed a layer between thewing 52 and the sensing device 20 has a significant coefficient ofinfrared absorption and therefore tends to block radiation transmittedfrom the wing 52 to the sensing device 20, so that less radiation fromthe underlying wing surface will be observed by the sensing device 20,and at the same time, that ice layer itself emits characteristicradiation from its surface, which will be observed by the sensing device20; (b) the accreted ice 60 will have added mass and thereby will haveadded heat capacity to the wing 52, and so will reduce the temperaturerise of the wing 52 relative to the temperature rise of the bare wing 52for a given quantity of thermal energy delivered by the heat inputimpulse 70; (c) the finite thermal diffusivity of the ice 60 results ina delay between the time of the thermal impulse 70 and the rise intemperature of the outer surface of the ice 60; (d) the ice 60 possessesa significant heat of fusion and therefore, for the case in which theinner surface of the ice reaches melting temperature, the temperaturerise of the ice layer, including the outer surface of the ice layerobserved by the sensing device 20, is delayed during the time that theinner surface of the ice layer is being converted to water. For thesereasons and/or other or different reasons, a thermal impulse to anice-bearing surface of the wing typically results in a time-dependentprofile of radiation, i.e., a temporal emission profile, from the wingin which the maximum value is smaller in magnitude and occurs later intime, relative to the time-dependent profile of radiation from thebare-wing surface.

The monitoring device 30 detects the presence of ice 60 or other debrison the surface of the wing 52 according to the change in radiationobserved from the wing 52. For example, the monitoring device 30 cancompare the change in emission of the wing 52 to a predeterminedcharacteristic, such as a predetermined value, rate, or temporal profileof radiation emission. According to one embodiment of the presentinvention, the profile characteristic is determined by a calibrationoperation in which a thermal impulse is initiated by actuating theheating device 40 at a time when ice is known to exist on the wing 52and, separately, at a time when the wing 52 is known to be bare. Themonitoring device 30 monitors the changes in the infrared radiationemitted and determines a profile characteristic that is representativeof the ice-bearing wing and a profile characteristic that isrepresentative of the bare wing. For a particular thermal impulse, theprofile characteristic can be a particular rate of increase or decreasein emission or a range of such rates, a multi-order or other complexprofile representative of the increase or decrease in emission, a timeor range of times for which the emission is above or below a particularvalue, and the like. It is understood that a variety of other profilecharacteristics can be determined including, for example, a maximumvalue, i.e., the peak height of the radiation emission curve of FIG. 4;the time interval between the thermal impulse and the maximum value orthe overall phase of the emission profile relative to a periodic thermalimpulse; the total radiation emitted from the wing 52, e.g., representedby the area defined by the emission profile and determined as anintegral of the emission profile; and/or other aspects of the shape ofthe emission profile. Further, the profile characteristic can bedetermined by theoretical or other methods. In particular, the profilecharacteristic can be determined as a function of the magnitude andduration of the heating impulse, the thermal characteristics of the wingmaterial, the presence and thermal characteristics of any debris on thewing 52, and the emissivity of the surface of the wing 52 and/or debrismaterial.

The monitoring device 30 can also be configured to communicate with theheating device 40 to initiate the operation of the heating device 40 ina pulsed diagnostic mode to test for debris on command. The monitoringdevice 30 can also actuate the heating device 40 according to apredetermined schedule to periodically test for debris. In particular,the monitoring device 30 can control the heating device 40 to initiateoperation of the heating device 40 for a predetermined interval andthereby initiate thermal impulses for heating the wing 52. For example,the monitoring device 30 can energize the heating device 40 during aninterval of between a fraction of a second and one or more minutes. Themonitoring device 30 can be configured to initiate such impulses inorder to determine the profile characteristics by the calibrationoperation described above.

Further, the monitoring device 30 can be configured to perform variousfunctions upon detection of ice 60 on the wing 52. For example, themonitoring device 30 can transmit an electronic signal to a statusindicator device 32 such as a visual or audible enunciator in thecockpit of the aircraft to alert the pilot or other crew members. Inaddition, the status indicator can be recorded as a data entry in aflight log or other record. The monitoring device 30 can also beconfigured to actuate the heating device 40 to automatically begin ade-icing process upon detection of the ice 60. While the heating device40 can be pulsed or otherwise selectively operated in the diagnosticmode, the heating device 40 in the de-icing mode can be operated toprovide sufficient thermal output for de-icing the wing 52, e.g., bycontinuously heating the wing 52 until any ice thereon is melted.

In one advantageous embodiment of the present invention, the sensordevice 20 is a multi-pixel device, and the monitoring device 30 isconfigured to independently detect the ice 60 on a plurality of portionsof the wing 52. The term “pixel” is not meant to be restrictive, and itis understood that each pixel can include one or more of the mostelementary sensing members of the device 20. Each pixel of the sensordevice 20 can be configured to sense the radiation emitted from acorresponding portion of the wing 52, and the monitoring device 30 canbe configured to monitor each pixel independently and detect ice on eachportion of the wing 52 according to profile characteristics of eachportion. Thus, the detection system 10 can be used to “map” the locationof the ice 60 on the wing 52. Further, once ice has been detected, themonitoring device 30 can control individual units of the heating device40, e.g., the individual resistive materials 42, so that the heatingdevice 40 heats those portions of the wing 52 that bear the ice 60. Insome embodiments of the present invention, multiple monitoring devices30 can be used to analyze spatially separate portions of a member.

FIG. 5 illustrates the operations of detecting debris on a surface of amember according to one method of the present invention. It isunderstood that some of the operations can be omitted and/or additionaloperations can be performed without departing from the presentinvention. For example, in Block 100, a heating device in thermalcommunication with the member is actuated to heat the member. Theheating device can be a de-icing system that is integral to an aircraftwing or other member, such as an electrical heating device or a systemfor directing hot gas through a passage in thermal communication withthe member. The resulting infrared radiation that is emitted from themember is sensed. See Block 110. If the member is part of an aircraft,the radiation can be sensed during flight or while the aircraft is onthe ground. Subsequently, the characteristics of the observed temporalprofile of the infrared radiation are analyzed to determine if debris ispresent on the member. See Block 120. For example, a profile of theradiation that is emitted from the member can be determined, and theprofile can be compared to a predetermined profile characteristic, whichcan be determined by actuating the heating device and sensing theinfrared radiation at a time when debris is known to exist on themember. Upon detection of ice or other debris on the member, the heatingdevice can be automatically actuated, and/or an electronic signal can becommunicated to a status indicator device. See Block 130.

Many modifications and other embodiments of the invention set forthherein will come to mind to one skilled in the art to which thisinvention pertains having the benefit of the teachings presented in theforegoing descriptions and the associated drawings. Therefore, it is tobe understood that the invention is not to be limited to the specificembodiments disclosed and that modifications and other embodiments areintended to be included within the scope of the appended claims.Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation.

1. A method for detecting ice on a surface of an aircraft, the methodcomprising: heating the surface as a diagnostic measure by activating ade-icing device integral to the aircraft and in thermal communicationwith the surface; independently sensing infrared radiation emitted froma plurality of portions of the surface; and determining changes in theinfrared radiation emitted from the plurality of portions resulting fromthe heating of the surface by the de-icing device in the heating step todetermine an emission profile for each of the portions and therebydetect the presence of ice on the surface of one or more portions,wherein the emission profile of a respective portion is based upon theradiation emitted from the respective portion.
 2. A method according toclaim 1 wherein said heating step comprises electrically energizing anelectrical de-icing device.
 3. A method according to claim 1 whereinsaid heating step comprises directing a flow of hot gases through apassage in thermal communication with the surface.
 4. A method accordingto claim 1 wherein said heating step extends for a predeterminedinterval of time.
 5. A method according to claim 1 wherein saiddetermining step comprises comparing the profiles to predeterminedprofile characteristics and thereby detecting the presence of ice on theportions.
 6. A method according to claim 5 further comprising, beforesaid heating step: actuating the de-icing device and thereby heating thesurface at a time when ice is known to exist on the surface; sensing theinfrared radiation emitted from the plurality of portions of the surfacewith ice; and determining a change in the infrared radiation for eachportion and thereby establishing the predetermined profilecharacteristic for each portion.
 7. A method according to claim 1wherein said determining step comprises determining the profiles of theradiation emitted from the portions during said heating step.
 8. Amethod according to claim 1 wherein said determining step comprisesdetermining the profiles of the radiation emitted from the portionsfollowing said heating step.
 9. A method according to claim 1 furthercomprising performing at least one function of the group consisting ofactuating the de-icing device to a de-icing mode and transmitting anelectronic signal to a status indicator device upon detection of ice onthe surface.
 10. A method according to claim 1 further comprisingrepeating said heating, sensing, and determining steps according to apredetermined schedule.
 11. A method of detecting ice on a surface of amember, the method comprising: a first heating step comprising heatingthe member at a time when ice is known to exist on the member; aftersaid heating step and while the ice is known to exist on the member,sensing infrared radiation emitted from the member and determining achange in the infrared radiation to thereby establishing a predeterminedprofile characteristic of the member; a second heating step comprisingheating the member by actuating a de-icing system integral to the memberand in thermal communication with the member; after a start of saidsecond heating step, sensing an infrared radiation emitted from aportion of the surface of the member opposite the de-icing system duringa time interval; and determining a temporal emission profile of theradiation emitted from the portion of the member during the timeinterval and comparing the temporal emission profile of the member tothe predetermined profile characteristic to thereby detect the presenceof ice on the surface of the member.
 12. A method according to claim 11wherein said determining step comprises comparing the profiles topredetermined profile characteristics and thereby detecting the presenceof ice on the portions.
 13. A method according to claim 11 wherein saiddetermining step comprises determining the profiles of the radiationemitted from the portions during said heating step.
 14. A methodaccording to claim 11 wherein said determining step comprisesdetermining the profiles of the radiation emitted from the portionsfollowing said heating step.
 15. A method according to claim 11 furthercomprising performing at least one function of the group consisting ofactuating the de-icing device to a de-icing mode and transmitting anelectronic signal to a status indicator device upon detection of ice onthe surface.
 16. A method of detecting ice on a surface of a member, themethod comprising: sensing emissions of an infrared radiation from thesurface of the member; heating the member during a time interval if thesensed emissions are below a characteristic temporal emission profile;sensing emissions of the infrared radiation from the surface of themember during the time interval; and determining a change in theinfrared radiation resulting from the heating of the member in saidheating step, and thereby detecting the presence of ice on the surfaceof the member.
 17. A method according to claim 16 wherein saiddetermining step comprises comparing the profiles to predeterminedprofile characteristics and thereby detecting the presence of ice on theportions.
 18. A method according to claim 16 wherein said determiningstep comprises determining the profiles of the radiation emitted fromthe portions during said heating step.
 19. A method according to claim16 wherein said determining step comprises determining the profiles ofthe radiation emitted from the portions following said heating step. 20.A method according to claim 16 further comprising performing at leastone function of the group consisting of actuating the de-icing device toa de-icing mode and transmitting an electronic signal to a statusindicator device upon detection of ice on the surface.